Selective metal binding by Vanabin2 from the vanadium-rich ascidian, Ascidia sydneiensis samea

Norifumi Kawakami, Tatsuya Ueki, Koichi Matsuo, Kunihiko Gekko, Hitoshi Michibata

研究成果: Article査読

25 被引用数 (Scopus)

抄録

Vanadium-binding proteins, or Vanabins, have recently been isolated from the vanadium-rich ascidian, Ascidia sydneiensis samea. Recent reports indicate that Vanabin2 binds twenty V(IV) ions at pH 7.5, and that it has a novel bow-shaped conformation. However, the role of Vanabin2 in vanadium accumulation by the ascidian has not yet been determined. In the present study, the effects of acidic pH on selective metal binding to Vanabin2 and on the secondary structure of Vanabin2 were examined. Vanabin2 selectively bound to V(IV), Fe(III), and Cu(II) ions under acidic conditions. In contrast, Co(II), Ni(II), and Zn(II) ions were bound at pH 6.5 but not at pH 4.5. Changes in pH had no detectable effect on the secondary structure of Vanabin2 under acidic conditions, as determined by circular dichroism spectroscopy, and little variation in the dissociation constant for V(IV) ions was observed in the pH range 4.5-7.5, suggesting that the binding state of the ligands is not affected by acidification. Taken together, these results suggest that the reason for metal ion dissociation upon acidification is attributable not to a change in secondary structure but, rather, that it is caused by protonation of the amino acid ligands that complex with V(IV) ions.

本文言語English
ページ(範囲)1096-1101
ページ数6
ジャーナルBiochimica et Biophysica Acta - General Subjects
1760
7
DOI
出版ステータスPublished - 2006 7月
外部発表はい

ASJC Scopus subject areas

  • 生物理学
  • 生化学
  • 分子生物学

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